The F-POD technology is unique among acoustic loggers, as they are based on high-resolution time-domain signal processing.
The F-POD uses the highest sampling rate of any commercial logger at 1million samples per second. This is upsampled in real time to 4million samples per second.
Time-domain analysis is performed using parallel processing to enable the key features of clicks to be identified and used as the basis for selecting what is worth storing and what details should be stored. This achieves selective data compression by >1000x with very little loss of useful data.

The angle-from-vertical is recorded each minute, enabling the user to check after deployment that the F-POD was deployed in a vertical position, and giving information on currents.
A range of angles at which the POD will log can be set.

This allows the F-PODs to be set up well in advance and transported in a horizontal attitude saving power and memory.

12 alkaline D-cells: 4.5-6 months
10 alkaline D-cells: 4-5 months
4 alkaline D-Cells (LF-POD): 6 weeks
10 Lithium primary D-cells: 9 months
25 Lithium rechargeable 21700 cells: over 8.5 months
10 Lithium rechargeable 21700 cells: over 4 months

(Note: Lithium D-cells that deliver <2v give massive noise levels). F-PODs can be set to log 1 minute in 2 or 5 or 10 minutes to further extend deployment time. Alternate minutes nearly doubles the overall logging duration.

Standard battery packs hold 12 D-cells (older versions took 10 D-cells). The battery housing is sprung in both directions to reduce battery damage from end impacts.

Lithium rechargeable: 25 x 21700 or 10x 21700 cells - these must be bought locally.

10 D-cell F-POD: Approximately +0.7 kg with alkaline D-cell batteries and +1.2 kg with lithium D-cells. This makes F-PODs self-orientating and increases the chance of recovery if the mooring fails.

Deep F-POD: -3.1 kg, not buoyant.

Coherent click trains are extracted and classified in post-processing by the KERNO-F classifier. 'Coherence' means having sequentially similar click features and inter-click-intervals through the train.

Version 1.0 is now in use and will be retained unchanged to give long term uniformity of performance if a major upgrade is released.

Digital time domain waveform analysis is used to select possible cetacean or boat sonar clicks in the range 20-220 kHz.

On-board train detection selects clicks in trains so that greater detail of some clicks can be captured.

The sensitivity of acoustic loggers is a major factor in determining the sea area within which animals are detected. In most studies using them, uniformity of sensitivity is essential and Chelonia tests and standardises each hydrophone.

Maximum detection range for porpoises is approximately 400 metres. Dolphins may be detected at >1 km.

Mean distance at detection is generally less than half the maximum, and effective detection radius is smaller again due to the narrow sound beam of clicks.

12 D-cell F-POD
Length: 745mm
Diameter: 90 mm
Weight: 2.3 kg without batteries
Weight: 3.85 kg with batteries

Lithium rechargeable F-POD
Length: 745mm
Diameter: 90 mm
Weight: 2.35 kg without batteries
Weight: 4.05 kg with batteries

Lithium rechargeable LF-POD
Length: 380 mm
Diameter: 90mm
Weight: 1.45 kg without batteries
Weight: 2.1 kg with batteries.

10 D-cell Deep F-POD
Length: 710 mm
Diameter: 100 mm
Weight: 7.15 kg without batteries
Weight: 8.6 kg with batteries

10 D-cell F-POD
Length: 710mm
Diameter: 90 mm
Weight: 2.1 kg without batteries
Weight: 3.5 kg with batteries

4 D-cell LF-POD
Length: 355 mm
Diameter: 90mm
Weight: 1.3 kg without batteries
Weight: 1.9 kg with batteries.

F-POD: Polypropylene.

Deep F-POD: Aluminium.

A web link engraved on the outside of the housing has enabled over 150 PODs to be returned to their owners by people who have found them on sea shores, sometimes more than 2,500 km from home!

The frequency range is 20 kHz to 220 kHz. The housing has a large diameter to reduce surface noise pick-up.

The transducer mounting and housing design gives exceptionally high resistance to impact damage.

The external surfaces of the F-POD are simple and tough allowing robust methods of removing biofouling.

The lids use a dual O-ring design with grease-free lubricants and these have proved highly reliable.

Any blank micro SD card up to 32 GB can be used.
Data volumes are typically 2GB in 4 months, or less, pro-rata, if alternate minutes or less are logged.

Intermittent logging is typically used to get logging periods of over 1 year.

F-POD: 3 x 10 mm holes in the lid that allow a very simple reliable lacing pattern where the end is put under the adjacent line between holes.

Deep F-POD: 1 x 12 mm hole in the lid.

The default settings cover all species and environments. Standard alternatives are available for river dolphins, noisy environments etc.

The F-POD has a dynamic threshold adaptation process to optimise performance during noisy periods.

The F-POD app (FPOD.exe) carries out automated data analysis (the KERNO-F classifier) to find click trains in the data and identify those produced by dolphins, porpoises and all echo-locating cetaceans except sperm whales.

The app displays, filters, analyses and exports this data and is free, with free upgrades.

The prallel processor runs two independent sonar detectors that detect and filter out boat sonars in real time.

These start anew each minute and keeping a record within the data of these sonar detections.

Porpoises and other narrow-band high frequency (NBHF) species can be distinguished from broadband species.

Every species tested has shown good detection performance.

Temperature is recorded each minute.

F-POD: the polypropylene housing goes to at least 100 metres.

Deep F-POD: At least 2 km.

An integral acoustic release is in development.

It is an alternative form of lid and has a tether line of up to 150m with 160kg breaking strain.

A means of streaming data via a 4G network to the cloud is under development with a plan to give near real time detection data to the user's PC.